Objective energy performance assessment of buildings is crucial for building stakeholders' rational decision making. One of the most popular building energy performance measures is Energy Use Intensity (EUI, kwh/m2.yr). This has been widely used since it is straightforward, simple and easy to understand. However, it has a severe drawback that it only shows the number of consumed energy per unit floor area and can't represent objective energy performance of a building. In other words, EUI does not deliver how well a building serves occupants and provides satisfactory services (e.g. thermal comfort). It is often misinterpreted in a way that the less EUI, the better building energy performance is. In this paper, a Data Envelopment Analysis (DEA) was applied to assess objective building energy performance. The DEA quantifies performance of a given system when multiple inputs and outputs are given. The DEA is a data-oriented and non-parametric method. Thus, it does not require any energy model and can consider multivariate inputs/outputs simultaneously. For the study, a number of virtual buildings were generated out of Monte-Carlo sampling and then simulated using EnergyPlus to derive a data set. Energy consumption was used as an input and building service levels (e.g. occupancy density [people/m2], operation time [hrs/yr], thermal comfort [PPD]) were used as outputs. It is shown that the DEA is a more objective and rational performance assessment method than the EUI, and can be a good alternative for building energy performance evaluation.